The Republic of Ireland midfielder McCarthy has been linked with the likes of Liverpool and Arsenal and Martinez claimed after the midfielder's two-goal performance in last weekend's 2-2 Barclays Premier League draw with QPR that the 22-year-old had "the potential to play anywhere in the world''.
The Spaniard added that "whenever he's ready we'll never stop him'' from leaving the club, but Martinez stressed McCarthy is still developing and says the distraction of transfer talk is the last thing the Republic of Ireland international needs.
He nodded when questioned whether or not he thought McCarthy would remain a Wigan player for the remainder of the campaign.
Asked if there had been any firm interest in McCarthy, Martinez said: "No."
“We will always feel really pleased with compliments towards our players,” he said.
"But James McCarthy is a young man - at 22 he is still developing.
"One day he will be challenging to win titles and to be in the highest position in the game, there is no two ways about it.
"But he is still developing and the performance that he had on Saturday shows that he is developing in the right way.
"He knows that and he knows as well that it is an important time for his role with the national team.
"The last thing he needs now is to be distracted from his good work and the way he is developing.''